The present invention relates to apparatus and methods for casting anchors in concrete units and, more particularly, for apparatus and methods for casting anchors in conrete units such that the anchor head is recessed within a void formed in the cast unit.
Many buildings and retaining walls include in their structure large, precast concrete units of various shapes designed to facilitate their interlocking engagement when set into place. These precast concrete units may range in weight from several hundred pounds to several tons. In order to facilitate the handling of such concrete units, the units are cast with pickup bolts or anchors at predetermined locations. The anchors typically comprise a length of steel rod with a flared head and foot. The flared foot may be tied to an adjacent piece of reinforcing steel, and the flared head is positioned within a void or recess so that it is spaced from the adjacent outer surface of the unit.
A precast concrete unit having the aforementioned anchors can be picked up and handled relatively easily by attaching the anchors to the cable of a hoist. The cable may be attached to lifting eyes which comprises a notched ball shaped to fit within the recess and engage the anchor head, and a large eye which is connected to a hook or cable. A lifting eye of this type is shown in Haeussler et al. U.S. Pat. No. 4,398,762.
One device for casting an anchor in a concrete unit is shown in Haeussler U.S. Pat. No. 4,296,909, and includes a pair of quarter-spherical steel elements which meet to form an opening sized to receive the shank of the anchor, and include an interior cavity recess shaped to receive the anchor head. The spherical elements are pivotally attached to a bridge piece which in turn receives a threaded mounting rod.
An anchor is inserted between the spherical elements and the rod is bolted to the formwork. The pressure of the formwork against the spherical elements and the bridge piece maintains them in a coplanar relationship to each other while the concrete is cast and hardens. After the concrete has hardened, the formwork is separated from the cast unit, and the device is disengaged from the anchor head by rocking the rod back and forth, which alternately disengages each of the quarter-spherical elements.
In another type of apparatus for casting an anchor, a hemispherical steel recess plug is attached to the formwork and includes a cylindrical recess sized to receive the anchor head. A split rubber ring is placed about the shank of the anchor just below the head and is sized to seal the cylindrical recess to prevent the entry of concrete during the casting process. Once the concrete has hardened, the formwork is separated from the cast unit, and the recess plugs are then manually removed from the units.
In a variation of the aforementioned device, the recess plug is made of rubber and includes a cylindrical opening sized to receive the shank of the anchor. The cylindrical opening communicates with an interior chamber shaped to receive the anchor head. This recess plug is attached to the formwork and the anchor is forced through the resilient cylindrical opening of the recess plug.
A disadvantage with this particular device is that there is a likelihood that the rubber recess plugs may be damaged after repeated deformation resulting from the forced insertion of the anchor head through the cylindrical opening. There is also a possibility of concrete leakage into the interior chamber in the event that the opening is not sized properly.
A disadvantage with all of the aforementioned devices is that the attachment of the anchor to the device, and the subsequent removal of the device from the anchor cast into the unit, are manually intensive, requiring an undesirable number of manipulative steps. This requirement for several manipulative steps raises the overall cost of fabricating the precast concrete unit. Accordingly, there is a need for an apparatus and method for casting an anchor in a concrete unit which is reliable, which minimizes the leakage of concrete into the void formed about the anchor head, and which minimizes the number of manipulative steps required for attachment of the anchor to the device and the subsequent removal of the device from the anchor cast in the unit.